Foot operated potentiometer and switch



Oct. 5, 1965 J. R. GOFF 3,210,712

FOOT OPERATED POTENTIOMETER AND SWITCH Filed April 25, 19 4 Sheets-Sheet 1 m ww INVENTOR. E 0FF Jaw * 5 M mmw y ArmQ/VEKS.

N E w m wm m w k Q R m Q V I mm s h mm W & Y h in h MN Q w i Q W MK m m LA W m M x W s Q 1% 9 Q UQ lQ Oct. 5, 1965 J. R. GOFF FOOT OPERATED POTENTIOMETER AND SWITCH Filed April 25, 1963 4 Sheets-Sheet 2 INVENTOR. {g3 L/UHN- R. 60H 1 sflm w Arrow 5m Oct. 5, 1965 J. R. GOFF FOOT OPERATED POTENTIOMETER AND SWITCH Filed April 25, 1963 4 Sheets-Sheet 3 F m R N E m6 f v0 4 N 1N Oct. 5, 1965 J. R. GOFF FOOT OPERATED POTEN'I'IOMETER AND SWITCH 4 Sheets-Sheet 4 Filed April 25, 1963 INVENTOR. BY L/0/-//\/ P. GoFF ATTOIZA/EYS.

United States Patent 3,210,712 FOOT OPERATED POTENTIOMETER AND SWITCH John R. Goff, Alsip, Ilh, assignor to Dreis 1 Krump Manufacturing (10., Chicago, 111., a corporation of Illinois Filed Apr. 25, 1963, Ser. No. 275,653 6 Claims. (Cl. 338-498) The invention relates to a new and improved accelerator control device including certain new and improved features of design and operation which in their preferred form are specially useful as a foot operated switch device permitting multi-directional variable control.

The control device in the form to be described has par ticular utility for use by an operator of a hydraulic press or the like in variably controlling the speed of operation of the press. In heavy duty metal forming hydraulic presses it has been conventional to provide a hand operated accelerator control which is effective in varying the speed of operation of the press. For example, a standard form of heavy duty press may include a hydraulic speed control mechanism to speed up or slow down press operation or may include a mechanical brake mechanism controlled by a servo system for application. Ordinarily brake application is controlled through an appropriate electrical servo system circuit including an adjustable potentiometer which is hand operated and which by voltage variation control of brake application regulates the speed of press opening or closing, as the case may be, when the press is in operation. Under conventional press operating procedures, it has been necessary for the operator to handle the metal workpiece as well as the press speed regulation control simultaneously. Where the workpieces are large and/ or heavy, it is laboriuous if not exceedingly difficult and hazardous for the operator to maintain positional control over the workpiece while simultaneously adjusting the speed of operation of the press by hand.

It is an object of the present invention to provide a new and improved accelerator control device including uniquely cooperating elements providing for variable operational control of presses or the like in a new and improved manv ner.

A further object is to provide a new and improved multiple purpose control device capable of multiple variable element operation and including a unique and compact arrangement of elements.

Still another object is to provide a new and improved fot operated accelerator switch device particularly adapted for use with hydraulic presses or the like, the device being of compact design and capable of multi-purpose efficient operation for use in controlling the opening and closing speeds of presses.

Another object is to provide a new and improved foot operated accelerator switch device particulary adapted for use with hydraulic presses or the like, the device including multi directional operating means for selective element actuation, the elements of the device being arranged for counterbalancing action in an efficient and uncomplicated manner.

Other objects not specifically set forth will become apparent from the following detailed description of the invention made in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective of the control device of the invention;

FIG. 2 is an enlarged fragmentary section of the device taken generally along line 22 in FIG. 1;

FIG. 3 is a transverse section of the device as viewed generally along line 3-3 in FIG. 2;

FIG. 4 is a fragmentary view of a portion of the device taken generally along line 4-4 in FIG. 3;

FIG. 5 is a fragmentary plan section of the device as viewed generally along line 55 in FIG. 2; and

FIG. 6 is a fragmentary view of the switch operating portion of the device illustrating operation thereof as compared to the position of the elements as shown in FIG. 3.

The control device of the invention generally comprises a variable potentiometer means having an operating means, which preferably is in the form of a reversibly rotatable shaft, projecting therefrom. The operating means is not only used to variably control the potentiometer means but is relied upon in the cam operation of separate switch means which in turn control energization of conventional pres control circuits including the variable potentiometer means. The operation of the switch means is brought about by the use of cam means mounted on the aforementioned operating means for movement therewith, the switch means including follower means engaging the cam means to control opening and closing of the switch means. While the following detailed description of the invention illustrates use of the basic design concepts thereof in a special foot operated switch device which also constitutes a part of the invention, it will be understood that the basic novel features of the control device have application in other specific forms of controls thus not limiting the use of the invention to the operation of hydraulic presses or the like.

FIG. 1 illustrates the accelerator switch device 10 as basically comprising a centrally located base member 11 having attached thereto a switch housing 12, a potentiometer housing 13, a bottom frame 14 and a cover plate 15. The base member 11 in the portion thereof which is exposed outwardly of the switch housing 12 has mounted thereon a foot treadle 16 carrying a pair of oppositely positioned, outwardly projecting foot pedals 17 and 13 which are located within the device to readily selectively receive the operators foot with the heel resting on an inclined plate section 19 forming a part of the bottom frame 14. The cover plate 15 is in the form of a shield with the top panel thereof projecting outwardly over the foot pedals 17 and 18 as best shown in FIG. 1 and including depending outwardly inclined side panel flanges 20 which extend below the foot pedals 17 and 18 outwardly thereof as also shown in FIG. 2. With this arrangement the operators foot is adequately confiend in the accessible portion of the device between the top and side flange panels of the cover plate 15, a top surface of a foot pedal 17 or 18, and the inclined heel plate 19. An operator either in the standing or sitting position can readily pivot his foot from one foot pedal to another for operation of the control device in the manner to be described.

As best shown in FIGS. 2 and 5, the base member 11 is in the form of a casting provided with a pair of spaced upstanding bosses 21 and 22, a transversely elongate rear section 23 provided with a centrally located transverse opening 24 therethrough, and an upstanding rear wall portion 25. The bottom frame 14 includes side wall portions 26 which at their ends are suitably attached by fasteners 27 to the outer side surfaces of the transverse section 23 of the base member as best shown in FIGS. 1, 3 and 5.

FIG. 2 illustrates the cover plate 15 supported by the wall portion 25 of the base member and attached to the rear face thereof by fasteners 28. The potentiometer housing 13 is of box shape and is attached by fasteners 29 to the cover plate 15. The bottom wall segment of the housing 13 overeXtends rear ear portions 30 (FIGS. 2 and 5) formed integrally with the base member, the

bottom portion of the housing 13 being attached thereto by leveling and support screw assemblies 31. The base member includes a plurality of longitudinally spaced leveling and support screw assemblies 31 for appropriate positioning of the control device for operational use. The switch housing 12 is of box-like configuration and is attached to the forward face of the rear upstanding wall portion 25 of the base member by fasteners 32. This housing is provided with a gasket sealedremovable front plate 33 suitably attached by fasteners 34 (FIG. and accessible under the cover plate 15.

' The housing 13 includes in the lower central portion thereof a dual or multi-stage potentiometer 35 which is of known type. The different stages of the potentiometer are identified by the separate series of lead posts 36 to which leads (not shown) of the press operating circuits are attached. The wire leads are fed into the housing 13 through a pair of aligned grommets 37 and 38 which are mounted in suitable openings in the upstanding rear wall portion 25 of the base member and rear Wall portion of the'switch housing 12 respectively. The wire leads for the different stages of the potentiometer 35 are selectively attached to control switches 39 and 40 (FIGS. 3 and 5) which include mounting plates 41 attached by fasteners 42 to the rear wall portion of the housing 12 for adjustable positioning relative thereto. Each switch 39 and 40 includes lead attachment means 43for leads extending to a selected stage of the potentiometer 35.

Basic operating circuit leads (not shown) are fed into the switch housing 12 through connector openings 44 (FIGS. 3 and 5) located in opposite side wall portions thereof. The right hand opening 44 as viewed in FIGS. 3 and 5 includes a known type of connector 45 received therein and having a protective grommet 46 through which circuitwiringis fed for selective connection'to the adjacent switch and one stage of the potentiometer. In hydraulic press application, one of the switches controls opening and closing: of a control circuit governing the opening of the press and the other switch controls the opening and closing of a control circuit governing the closing of the press. When either switch is closed, the particular stage of the potentiometer 35 to which it is connected is then placed in operation in the selected control circuit to vary the speed of the press during opening or closing thereof.

The rear surface of the upstanding wall portion 25 of the base member has suitably mountedthereon a pair of contact blocks 47 (FIGS. 2 and 5) which provide for proper electrical alignment of the various leads of the rather complex press control circuits. Among other things these blocks 47permit electrical connection of control potentiometers 48 and 49 (FIG. 5) which are located in the potentiometer housing 13 mounted on a U-shaped bracket 50 which is attached to outwardly projecting bosses 51 formed on the rear surface of the wall portion 25. Fasteners 52 attach the bracket 50 to the bosses 51. The control potentiometers 48 and 49 include lead posts 53 for use in connecting the same in the press circuits and selectively to the stages of the potentiometer 35. The control potentiometers 48 and 49 include adjusting shafts 54 which are readily available for tool engagement upon removal of the housing 13. These control potentiometers are pre-set to control the voltage range of operation of the individual stages of the main dual potentiometer 35- depending upon press operational requirements.

The potentiometer 35 includes an operating shaft 55 which as best shown in FIG. 2 is rotatably journaled in aligned openings extending longitudinally of the base member 11 through the rear wall portion 25 and bosses 21 and 22. The shaft 55 constitutes the operating shaft of the potentiometer 35 and with the potentiometer is supported in the housing 13 on the bracket 50. This operating shaft, as is conventional with multi-stage potentiometers, simultaneously operates both stages of the potentiom'eter upon rotation in clockwise or counterclock- Wi e direct n t e e e t veness of the adjustment of either stage of the potentiometer depending upon whether such stage is actually coupled in an operating circuit. The selective coupling of either stage of the potentiometer 35 depends upon operation of the switches 39 and 40 in a manner to be described. The shaft 55 includes with the outer end thereof a lubricating nipple 56 in communication with a central passage 57 (FIG. 3) extending longitudinally of the shaft and in turn in communication with a plurality of radial ports 58 (FIG. 2) extending to outer surface circumferential grooves 59 which are longitudinally located to provide lubrication in the journal openings of the base member 11.

As best shown in FIGS. 2 and 5, the foot treadle 16 extends transversely of the shaft between the bosses 21 and 22 and between washers 60 fixed to the shaft, and a set screw 61 fixes the treadle and attached pedals 17 and 18 to the shaft thus providing for reversible rotation of the shaft as a result of operating pressure applied to the foot pedals 17 and 18. Between the boss 22 and the rear wall portion 25 Within the transverse opening 24 the shaft has fixed thereto a cam block 62 carrying a set screw 63. This cam block as best shown in FIG. 3 is wingshaped and includes a pair of oppositely positioned, outwardly projecting cam shoulder portions 64 provided with upwardly exposed convex camming surfaces 65. With this arrangement the cam block 62 will rock with the shaft 55 in response to selective foot pedal depression. Correspondingly, the stages of the potentiometer 35 will be variably adjusted.

Referring specifically to FIG. 3, each cam shoulder portion 64 has operatively associatedtherewith a vertically extending follower pin 66 which extends upwardly through a journal member 67 in the bottom wall of the switch housing 12, the upper end portion of each follower pin being journaled in a member 68 carried in the top wall portion of the housing 12. The pins 66 are arranged for vetrical reciprocation through the housing 12 and between the journal members 67 and 68 carry spring retaining and switch camming sleeves 69 which are fixed by transverse pins 70 to the follower pins for vertical reciprocation therewith. The bottom surface 71 of each sleeve 69 is arranged for flat abutment with the top is seated at its bottom end against an inner shoulder portion of the sleeve 69 and 'at its top end against the. bottom surface of the journal member 68. The spring 72- is compressed to constantly urge the follower pin downwardly to maintain the sleeve 69, in abutment with the journal member 67 and the bottom end of the pin 66 in engagement witha cam shoulder portion 64 in the neutral position of the shaft 55 as shown in FIG. 3. The bottom end of each follower pin 66 is rounded to permit ready sliding engagement along the engaged camming surface Each sleeve 69 at its top outer end is provided with a frusto-conical camming surface 73 which in the neutralposition of the follower pin as shown in FIG. 3 is in engagement with a spring held plunger 74 constiutingthe operating member of one of the switches 39 and 40,. These switches are of conventional type, preferably micro swtiches, and are closed upon adequate depresssion of the operating plungers 74 thereof.

In the operation of the device 10, the operator will selectively depress one of the foot pedals 17 or 18 thus providing for rotational movement of the shaft. 55 accompanied by rocking of cam block 62 and a lifting of one of the follower pins 66. Simultaneous with this operation the potentiometer 35 will of course undergo adjustment. FIG. 6 illustrates the closing of the switch 40- upon depression of the foot pedal 17 and rotation of the shaft 55 in a counterclockwise direction as viewed. The follower pin 66 associated with the switch 39 will remain stationary by reason of abutment of the bottom surface 71 of the sleeve 69 with the top surface of the journal member 67. The bottom end of this follower pin will become separated from its associated cam shoulder portion 64 of the cam block 62. The follower pin 66 associated with the switch 40 will however slide along the convex camming surface 65 in engagement therewith and will be lifted substantially in the switch housing 12 with the upper end thereof projecting above the top surface of the journal member 68. During this lifting the sleeve 69 will of course move upwardly and the switch plunger 74 will be depressed by movement along the frusto-conical camming surface 73 onto the outer cylindrical surface of the sleeve 69. The switch 40 will thus be closed and the operating circuit of which it forms a part will be energized, this circuit including one of the stages of the potentiometer 35 thus providing for adjustable variation of the operation of this circuit and acceleration control of the press either during opening or closing thereof as the case may be.

In the foregoing respects the neutral position of the shaft 55 provides for center top positioning of the wiper arms of the potentiometer 35 and stopping of the press. Depression of one of the foot pedals 17 and 18 will provide for acceleration of the press to the degree to which the foot pedal is depressed either during opening or closing thereof. If the press should be fully closed and the operator should depress the foot pedal energizing the closing circuit portion, the press will remain closed and the operation need only move his foot to the opposite pedal for intended press opening operation. Control of acceleration of the opening and closing operations of the press solely by foot pressure permits the operator to use both hands in the handling of the workpiece being advanced into or removed from the press. This not only provides a substantial margin of safety but provides the operator with immediate control over press operations without necessitating partial releasing of the workpiece and reaching for press acceleration controls.

Upon the release of pressure applied to the foot pedals 17, the spring 72 of the follower pin 66 associated with the switch 40 will return the follower pin downwardly to its neutral position and in doing so will act on the cam block 62 to return the shaft to its neutral position thus also adjusting the potentiometer 35 to its neural position. Downward return movement of the follower pin 66 is controlled by abutment of the bottom surface 71 of the sleeve 69 with the top surface of the journal member 67. This prevents opposite directional rotation of the shaft 55 beyond its neutral position. During the downward return of the follower 66, the switch plunger 74 will again engage the camming surface 73 and will move outwardly to open the switch 40 thus breaking the operating circuit.

In order to prevent fluttering or bouncing of a follower pin in the event of fast downward return to the neutral position, each pin is provided with a spring operated safety detent arrangement illustrated in FIG. 4. The top portion of each pin 66 within the top journal member 68 is formed with a circumferential hemispherical groove 75 in which a ball detent 76 is received in the neutral position of the pin. The ball 76 is carried in a transverse passage 77 formed in the journal member 68 and is backed up by a coil spring 78 which is compressed by a set screw 79 threadedly received in the passage 77. Operating force applied to one of the foot pedals is sufficient to overcome the resistance established by the ball detent 76 and permit upward movement of the follower pin 66 in the manner previously described. Upon foot pedal pressure release and downward return of the follower pin, the ball detent 76 will engage the groove 75 and will exert sufficient force against the follower pin to prevent subsequent upward bouncing return. The upward return can be caused by a striking of the bottom surface 71 of the sleeve 69 against the upper surface of the bottom journal member 67 with sufficient force so that 6 the reaction will overcome the spring 72 and the follower pin will bounce upwardly.

The particular structural arrangement described is relatively uncomplicated and is capable of efiicient troublefree operation. This arrangement is quite compact and yet is subject to ready maintenance when necessary. The use of the spring mounted follower pins in combination with the cam block carried by the potentiometer operating shaft among other things permits a self-balancing effect which functions to maintain the control device in its neutral inoperative position. Not only does the detent arrangement of FIG. 4 aid in preventing multi-directional return or fluttering upon operational pressure release, but the inoperative follower pin 66 will engage its respective cam shoulder portion upon the return of the shaft to its neutral position as urged by the other follower pin and will aid in preventing over center movement of the shaft.

While the device has been described in conjunction with the use of a dual or multi-stage potentiometer 35, it will be understood that a single stage center tap potentiometer can be used to advantage. With such a potentiometer the operating shaft 55 will move the wiper arm to either side of the center tap to vary the voltage used in driving one of the control circuits. With this arrangement any inherent voltage variations existing between dual stages are eliminated and press speed is equally variable during both opening and closing.

Obviously certain modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A control device comprising a potentiometer having a reversibly rotatable operating shaft extending therefrom, operating means for said shaft, a cam block fixed to said shaft and included oppositely positioned transversely projecting cam shoulder portions each provided with a camming surface, cam follower pins mounted for reciprocation and in engagement with said camming surfaces in the neutral position of said shaft, spring means urging said shaft to said neutral position, a switch including operating means associated with each of said follower pins, and cam means on said follower pins engaging the operating means of a switch to open the same in the neutral position of said shaft and close the same upon selected movement of said follower pin, each switch being connected to said potentiometer to energize the same upon closing of said switch.

2. The control device of claim 1 wherein said spring means are engaged with said follower pins to maintain end portions thereof in engagement with said camming surfaces in the neutral position of said shaft, and in the absence-of an operating force applied to said shaft to balance said cam block to maintain said shaft in the neutral position.

3. The control device of claim 1 wherein each follower pin is provided with a spring means urging the same into engagement with a camming surface, each follower pin including stop means limiting movement thereof toward a camming surface, and spring actuated detent means engaging each follower pin to prevent return movement thereof upon operation of said stop means in the absence of effective operating force applied to said shaft.

4. A foot operated accelerator switch device comprising a housing, a potentiometer in said housing having a reversibly rotatable operating shaft extending therefrom and rotatably journaled through a portion of said housing for access thereto externally of said housing, a foot treadle fixed to said shaft externally of said housing for opposite directional rotation of said shaft, a cam block fixed to said shaft within said housing and including oppositely positioned transversely projecting cam shoulder portions each provided with a top convex camming surface,

vertically extending cam follower pins mounted in said housing through journal means for reciprocation and in engagement with said camming surfaces in the neutral position of said shaft, spring means urging said shaft to said neutral position, a switch including operating means associated with each of said follower pins, and cam means on said follower pins engaging the operating means of a switch to open the same in the nuetral position of said shaft and close the same upon upward movement of a follower pin, each switch being connected to said potentiometer to energize the same upon closing of said switch.

5. The accelerator switch device of claim 4 wherein said spring means are engaged with said follower pins to maintain the bottom end portions thereof in engagement with said camming surfaces in the neutral position of said shaft, and in the absence of an operating force applied to said foot treadle to balance said cam block to maintain said shaft in the neutral position.

6. The accelerator switch device of claim 4 wherein each follower pin is provided with a spring means urging the same into engagement with a camming surface, each follower pin including stop means limiting downward movement thereof, and spring actuated detent means engaging each follower pin to prevent upward return movement thereof upon operation [of said stop means in the absence of effective operating force applied to said foot treadle.

References Cited by the Examiner UNITED STATES PATENTS 505,063 9/93 Ramien 338153 X 603,524 5/98 Coachman 338l53 X 682,347 9/01 Sims 74512 1,242,357 10/17 Ljungstrom 338-200 X 2,531,764 11/50 Binus et al 338-153 X RICHARD M. WOOD, Primary Examiner. 

1. A CONTROL DEVICE COMPRISING A POTENTIOMETER HAVING A REVERSIBLY ROTATABLE OPERATING SHAFT EXTENDING THEREFROM, OPERATING MEANS FOR SAID SHAFT, A CAM BLOCK FIXED TO SAID SHAFT AND INCLUDED OPPOSITELY POSITIONED TRANSVERSELY PROJECTING CAM SHOULDER PORTIONS EACH PROVIDED WITH A CAMMING SURFACE, CAM FOLLOWER PINS MOUNTED FOR RECIPROCATION AND IN ENGAGEMENT WITH SAID CAMMINE SURFACES IN THE NEUTRAL POSITION OF SAID SHAFT, SPRING MEANS URGING SAID SHAFT TO SAID NEUTRAL POSITION, A SWITCH INCLUDING OPERATING MEANS ASSOCIATED WITH EACH OF SAID FOLLOWER PINS, AND CAM MEANS ON SAID FOLLOWER PINS ENGAGING THE OPERAITNG MEANS OF A SWITCH TO OPEN THE SAME IN THE NEUTRAL POSITION OF SAID SHAFT AND CLOSE THE SAME UPON 